difficulty是名词，没有比较级，一般比较级是指形容词或副词才有比较急。

那么difficulty名次的形容词变体是difficult，difficult的比较级是more difficult表示更难的，例如：

1. While the top of the ocean is well studied, its depths are more difficult to explore.虽然海洋表面已得到了充分的研究，但深海更难探索。

2.Exercise energizes you, so it is more difficult to relax and have a peaceful sleep when you are very excited ．运动使你精力充沛,所以当你非常兴奋的时候会更难放松和进入睡眠。